The character was originally based on Seinfeld co-creator Larry David, but surnamed after Jerry Seinfeld's real-life New York friend, Mike Costanza. Alexander reprised his role in an episode of Comedians in Cars Getting Coffee, reuniting with Jerry Seinfeld and Wayne Knight (also reprising their roles as Jerry and Newman, respectively).

In the season four episode "The Junior Mint", he states he grew up in Brooklyn, New York, where he went to a public school.[8] In a previous episode he mentions he went to high school on Long Island.[9] He met Jerry Seinfeld during his youth, and they remained friends from that point on.[10] George and Jerry both attended John F. Kennedy High School, class of 1971.[11] During their high school years, George and Jerry frequently hung out at a pizza place called Mario's Pizzas, where George, having the highest score 'GLC', would play Frogger.[12] George was picked on by his gym teacher Mr. Heyman (Biff Yeager), who intentionally mispronounced his name as "Can't stand ya" and gave him wedgies.[13]

George has three known cousins: Shelly, who appeared in "The Contest",[14] George Howarth, and Rhisa, who made an appearance in "The Junk Mail".[15] George talks to his parents about his family in "The Money", during which it is revealed that he had an "Uncle Moe", who "died a young man" and an "Aunt Baby", who died at the age of 7 of internal problems.[16] It is also revealed that his mother has a "Cousin Henny".[16] In "The Doll", it is revealed that Frank Costanza was born in Italy and has a cousin, Carlo, who still lives there.[17] As of the first-season episode "The Robbery", George had a living grandmother and grandfather whom he had recently visited, although it is never made clear whether these were his mother's or his father's parents.[18]

George is neurotic, self-loathing, and dominated by his parents, yet is also prone to occasional periods of overconfidence that invariably arise at the worst possible time. Throughout Seinfeld‍ '​s first season, George was portrayed as a moderately intelligent character – at one point, he mentions an intellectual interest in the American Civil War and, in some early episodes, appears almost as a mentor to Jerry – but becomes less sophisticated, to the point of being too lazy even to read a 90-page book (Breakfast at Tiffany's), preferring to watch the movie adaptation at a stranger's house instead. However, one Chicago Tribune reviewer noted that, despite all of his shortcomings, George is "pretty content with himself".[19]

George exhibits a number of negative character traits, among them stinginess, selfishness, dishonesty, insecurity, and neurosis. Many of these traits appear to stem from a dysfunctional childhood with his squabbling parents Frank and Estelle, and often form the basis of his involvement in various plots, schemes, and awkward social encounters. Episode plots frequently feature George manufacturing elaborate deceptions at work or in his relationships in order to gain or maintain some small or imagined advantage or (pretend) image of success. He had success in "The Opposite", in which he begins (with Jerry's encouragement) to do the complete opposite of what his instincts tell him to do, which results in him getting a girlfriend and a job with the New York Yankees. His neurosis is also evident in the episode "The Note", where he starts having doubts on his sexual orientation after receiving a massage from a male masseur.

George sometimes refers to himself in the third person (for example, "George is getting UPSET!"), after befriending a person with a similar trait in "The Jimmy".

George's occasional impulsiveness often gets him into trouble, such as when he flees a burning kitchen, knocking over several children and an elderly woman in the process, so he could escape first during his girlfriend's son's birthday party in "The Fire". However, there are moments where George exhibits remarkable courage, but usually accidentally and often in support of inane lies to which he would rather not confess. For instance, in "The Marine Biologist", he goes into the ocean alone to save a beached whale because his date, a woman he had a crush on in college, thinks he is a marine biologist and even tells her the truth about his occupation after he saves the day. However, this causes her to reject him immediately, and he is forced to take the bus home.

George often goes to impressive measures to build and maintain his relationships with women. In “The Conversion”, he goes through the process of converting to the Latvian Orthodox religion as his girlfriend’s conservative parents would not allow her to date someone outside their religion. In “The Susie”, he deems it so important that he make a grand entrance at his work’s ball with his attractive girlfriend Allison that, upon finding out that she plans to break up with him, George goes to great lengths to avoid her before the ball, stating "If she can't find me, she can't break up with me.” Ultimately though, the one relationship he holds long-term, with his fiancée Susan, is the one he is seemingly least enthusiastic about, as shown by his ongoing efforts to first to postpone, and later cancel, their wedding and his rather calm reaction when she suddenly passes away. In fact, in "The Foundation", George shows greater emotion while discussing the death of the Star Trek character, Spock, in the movie, "The Wrath of Khan" than he did after the death of Susan.

George aligns with both Elaine and Kramer in some episodes, but is also frequently pitted against them. With Elaine, while he does get into arguments with her, they also work together, most notably in the episode "The Cadillac", although George states in "The Dinner Party" that he is frightened of Elaine. George and Kramer usually feel awkward around each other, but started working together (and against each other) in episodes "The Busboy", "The Stall", and "The Slicer". "The Susie" is the only episode in which their relationship is as prominent as the relationships between the other characters. Some episodes, such as "The Raincoats", "The Money", "The Doorman", and "The Fusilli Jerry", would suggest that Kramer has a more comfortable rapport with George's parents than with George.

He has an interest in nice restrooms and his personal bathroom habits that borders on obsession. In "The Revenge", he quits his real estate job solely because he is forbidden to use his boss's private bathroom. In "The Voice", he admits that one of the reasons he is staying at a job from which his boss has asked that he resign (for faking a disability), is because it gives him "private access to one of the great handicapped toilets in the city". In "The Busboy", he claims to have an encyclopedic knowledge of the locations of the best public bathrooms in the city. He proves this in "The Bizarro Jerry" when he directs Kramer to "the best bathroom in midtown" at the offices of Brand/Leland, even describing the layout, marble, high ceiling and toilets that flush "like a jet engine". In "The Gymnast", he told Jerry that he always removes his shirt when using the bathroom because "it frees me up... no encumbrances". It is unclear if he dropped this habit after an embarrassing incident (also in "The Gymnast") in which he walked out of a bathroom shirtless at a lunch party attended by his girlfriend, girlfriend's mother and other female members of her family. When working for the Yankees, he suggested having the bathroom stall doors stretched all the way to the floor (allowing people's legs not to be seen while in the stalls), and, in many episodes, he shows a fascination with toilet paper and its history. He also displays a fear of diseases, such as lupus and cancer. In "The Wife", George gets into trouble for urinating in the shower at a gym but defends his action with, "It's all pipes! What's the difference?" even threatening to call a plumber to back him up.

Although occasionally referred to as dumb by his friends, many signs point to the fact that George is actually quite an intelligent man despite his neurotic behavior. George's foolishness is displayed in the episode, "The Cafe", in which George had to take an IQ test and had Elaine take it for him. Apparently, George's neurotic stupidity would progress until it became one of his primary characteristics. By the season six episode "The Couch", he could not even concentrate enough to read a 90-page book (Breakfast at Tiffany's). In "The Abstinence", it is discovered that George actually has what would appear to be genius-level intelligence, but that he can never access it because his mind is always so completely focused on sex. When circumstances allow him to temporarily remove sex from his mind, he is able to reach his true intellectual potential, solving a Rubik's Cube, answering a string of questions on Jeopardy!, and giving Derek Jeter and Bernie Williams pointers on hitting based on Newtonian physics.

George and Jerry have been best friends since meeting in high school gym class. The extreme closeness of their friendship is occasionally mistaken for homosexuality. "The Outing" deals with a reporter from a New York University college paper mistaking Jerry and George for a homosexual couple, and, in "The Cartoon", George dates someone whom Kramer insists is merely a "female Jerry". When George is forced to note to himself that the idea of a female Jerry with whom he can have a close personal relationship and also a sexual relationship would be everything he has ever wanted, George, in horror, breaks off his relationship with the woman.

Seinfeld co-creator Larry David based George largely on himself.[20][21] Seinfeld and David created the character as a counterpoint to Seinfeld's character.[22] In the first draft of the show's pilot script, called "Stand-Up" at the time, George's name was Bennett and he, like Jerry, was a comedian.[20] In that same draft, the scene in the pilot in which George and Jerry discuss a woman Jerry met earlier, saw George and Jerry discussing their stand-up act.[20] This idea however, was quickly abandoned and his name was changed to George, the real estate broker instead.[20] George's last name comes from Michael Costanza, a college classmate of Seinfeld.[23] "Louis", George's middle name is a homage to Lou Costello, whose 1950s television series The Abbott and Costello Show, inspired Seinfeld‍ '​s writing style.[24] Although he is often asked whether he wanted to play the character, Larry David has said that he was only interested in writing the show, that, not only did he not want to act on the show, but it had never occurred to him and, even if it had, he highly doubted that NBC would have approved of his being cast.[22]

Casting director Marc Herschfield stated that, during casting for the character, "we saw every actor we could possibly see in Los Angeles", but they could not find the right actor for the part.[22] Among the auditionees were Nathan Lane, Steve Buscemi, David Alan Grier, Brad Hall and Larry Miller.[20][25] On April 3, 1989, Herschfield sent a partial script to Jason Alexander, who was in New York City at the time.[22] Herschfield had met Alexander when he was working on the CBS sitcom E/R.[22] Alexander enjoyed the script and felt it read like a Woody Allen film; therefore, he did a Woody Allen impression on his audition tape, and bought a pair of glasses to better resemble the character.[22][26] Though Alexander thought his audition was "a complete waste of time", both David and Seinfeld were impressed; Seinfeld stated "the second we saw him, like two lines out of his mouth, we went 'That's the guy'".[22] On April 10, 1989 at 9:00 A.M. Alexander did his first official audition and met David and Seinfeld.[20] While in the waiting room for his final audition, Alexander saw that Larry Miller was also auditioning.[22] Alexander was aware that Miller and Seinfeld were very good friends, and so figured that he would not get the part. After his final audition he returned to New York City, and when he landed he received a phone call informing him that he was hired.[22]

Many of George's predicaments were based on David's past real-life experiences. In "The Revenge", for example, when George quits his job in a fury only to realize he has made a mistake, he goes back the next day as if nothing happened; this mirrors David's actions while working as a writer for Saturday Night Live, when he quit and then returned to his job in the same manner.[22] As the show progressed, Alexander discovered that the character was based on David. As Alexander explains in an interview for the SeinfeldDVD, during an early conversation with David, Alexander questioned a script, saying, "This could never happen to anyone, and even if it did, no human being would react like this." David replied, "What do you mean? This happened to me once, and this is exactly how I reacted." After that, Alexander changed his performance from an imitation of Woody Allen to what he has called a "shameless imitation of Larry David."

In 1998, Michael Costanza sued the show for US$100,000,000, claiming that he never gave permission for his name to be used and that, because of the character's appearance and behavior, he was not treated with respect.[27][28] Costanza lost the suit, as the New York Supreme Court (the trial court in the State of New York court system) decided that Seinfeld and David "did not violate Michael Costanza's privacy rights when they created the character".[29]

George becomes engaged to Susan Biddle Ross, a wealthy executive at NBC who approved Jerry and George's show-within-a-show sitcom pilot. George and Susan date for a year, during which time the commitment-phobic George is constantly trying to find ways to end their relationship without actually having to initiate the breakup with her. In "The Engagement", he proposes to her in a short-lived bout of midlife crisis, after he and Jerry make a pact to move forward with their lives. When Jerry breaks up with his girlfriend almost immediately thereafter for eating "her peas one at a time" and declares the deal over, George panics and again tries repeatedly to weasel out of his engagement. He gets his wish about two weeks before the wedding in "The Invitations", when he inadvertently causes her death by selecting cheap envelopes for their wedding invitations, not knowing they contained toxicglue. When notified of her death at the hospital, George displays a combination of shock, apathy, and relief (later described by the doctor in part two of The Finale as "restrained jubilation"). A few moments after being notified of Susan's passing, he says to Jerry, Kramer, and Elaine, "Well, let's go get some coffee." Susan's parents, recent divorcees, never knowing the specifics behind her poisoning but suspecting that George was somehow involved, never forgive him for this, and they appoint him to the board of directors of the Susan Ross Foundation to keep him trapped under their influence and to ensure that he would never get any of Susan's inheritance.

George is very bad at meeting women and even worse at maintaining his romantic relationships and, as a result, his relationships usually end badly.[30][31] George also dated other women throughout the series:

His two dates, Maura (who refuses to break up) and Loretta (who will not make love in "The Strongbox"), make it hard for George to break up.

In "The Cadillac", George goes on a date with actress, Marisa Tomei (who loves "quirky, funny, bald men"), in the park for a short time but gets punched after revealing that he is engaged.

In "The Cafe", George dates Monica, who tests George in an IQ test. Apparently, after letting Elaine help him cheat, the end result is the test being spilled with food, and he is left to explain about the mess on the IQ test.

In "The Nose Job", George dates Audrey, who has a big nose, until he, Jerry, and Elaine are shocked when Kramer suggests that she get a nose job.

In "The Red Dot", by accident, George dates Evie, a cleaning woman who works at Pendant Publishing by sharing Hennigans.

In "The Conversion", George willingly converts to the Latvian Orthodox faith for his girlfriend, Sasha, after Elaine mentions that it would be romantic, only to learn after completing the conversion that Sasha is going to Latvia.

In "The Boyfriend", George dates Carrie, the daughter of his unemployment-office rep, Mrs. Sokol, in order to get an extension on his unemployment.

In "The Good Samaritan", George commits adultery with a married woman, Robin, after he says "God bless you" to her.

In "The Outing", George dates Allison, who is having a breakdown. He tries to get out of the relationship by saying he's gay, but it fails.

In "The Cartoon", George dates Janet, who Kramer openly says looks like Jerry.

In "The Pez Dispenser" George dates a pianist, Noelle who wishes to break up with George after Elaine laughs during a recital. George has a telephone communication with Noelle and feels like she wishes to break up, so he breaks up with her first. Later at an intervention for an old friend of Elaine and Jerry's, Elaine laughs the laugh that Noelle will never forget and it is revealed she is the one that shattered Noelle's confidence during the recital.

In "The Fix-Up" George refuses a blind date with Cynthia until assured she meets his intellect (low) and attractiveness (high) standards (George: Is there a pinkish hue? Jerry: A pinkish hue? George: Yes, a rosy glow. Jerry: There's a hue. She's got great eyebrows, women kill to have her eyebrows. George: Who cares about eyebrows? Is she sweet? I like sweet. But not too sweet, you could throw up from that.")

In the season 7 Curb Your Enthusiasm episode "Seinfeld", George has married (and divorced) a woman named Amanda in the time since the finale. It is unclear, however, whether these events are considered canon in the Seinfeld series.

George's professional life is unstable. He is unable to remain in any job for any great length of time before making an embarrassing blunder and getting fired, and he is unemployed for a large amount of time throughout the series. Very often, the blunder is lying and trying to cover it up, only to have it all fall apart.

Over the course of the series, he works for a real estate transaction services firm (Rick Bahr Properties), a rest stop supply company (Sanalac), Elaine's company (Pendant Publishing), the New York Yankees (his longest running job), a playground-equipment company (Play Now), an industrial smoothing company (Kruger Industrial Smoothing), and other places. He is fired from his job at Pendant Publishing for having sex with the cleaning woman on his desk in "The Red Dot" (he professes he has always been attracted to cleaning women).

His original job when the series starts is as a real estate agent; he ends up quitting and getting re-hired, but fired immediately afterward for drugging his boss. He always wanted to be an architect or least "pretend to be an architect". He first mentions this desire in "The Stake Out", and he claims in "The Race" that he had designed "the new addition to the Guggenheim". In "The Van Buren Boys", he denies his young protégé a scholarship from the Susan Ross Foundation when the young man decides he no longer wants to be an architect and wants to become a city planner instead. In "The Marine Biologist", Jerry tells a woman whom George wanted to impress that George is a marine biologist. The plan backfires when George is called upon to save a beached whale with a Titleistgolf ball in its blowhole. He saves the whale, but the woman tells him off when he confesses that he is not, in fact, a marine biologist: "She told me to go to hell, and I took the bus home." He then gets a job working for the Yankees, where he frequently encounters a fictionalized version of Yankees owner George Steinbrenner (the voice of Steinbrenner is made by Larry David).

During the fourth season of the series, George gains experience as a sitcom writer as he helps Jerry to write the pilot for the fictitious show Jerry. While pitching the concept of a "show about nothing" to NBC executives, George dates executive Susan until "The Virgin", when she is fired. Following the first and last episode ("The Pilot"), executive Russell's obsession with Elaine has cost George and Jerry a shot at getting a TV series.

George is known for his balding hair, which is not as noticeable in the pilot episode "The Seinfeld Chronicles" or a flashback in "The Slicer", but gets thinner as the series progresses. In "The Beard", he begins to wear a toupee, until Elaine throws it out the window in disgust. He also attempts to restore his hair in "The Tape", when he begins using a Chinese cream that is said to be such a great cure for baldness that it will make him "look like Stalin". His hair is rarely seen styled. His clothes are usually very plain. He frequently wears jeans and Nike Cortez sneakers. In "The Pilot", George wears sweatpants; Jerry says that this makes George look like he has given up on life. In "The Subway", when his clothes are taken, he goes to the coffee shop with a blanket, causing a bystander to mistake him for a Hare Krishna. In "The Muffin Tops", he steals clothes from a tourist who asks him to watch his suitcase. "The Gum" has him dressed as Henry the Eighth, which, along with a far too small tuxedo in "The Opera", are the only times he is seen entirely apart from his drab attire. George has, however, mentioned that his clothing is color-coded based on his mood. In "The Trip", Jerry asks him what mood he is in, and George replies, "Morning mist". Several times throughout the show, George mentions a desire to "drape" himself in velvet (if only it were socially acceptable), which he does in "The Doodle". In the episode "The Bizarro Jerry", George can be seen styling his hair based on an Andy Sipowicz (Dennis Franz) poster.[32] His clothing on the show was usually a size too small for him, as opposed to Kramer, whose clothes were usually a size too big.

Art Vandelay is first referenced in the episode "The Stake Out", in which George and Jerry need an excuse to give to a woman as to why they are waiting in the lobby of the office building where she works. Their excuse is that they were meeting Art Vandelay, an importer-exporter who works in the same building, for lunch. In one instance ("The Boyfriend"), George tells the unemployment office he is close to getting a job at "Vandelay Industries", a latex manufacturer. The name is also used as a fake boyfriend of Elaine. Here, Art is an importer/exporter and used as a cover story for when George is going on a date with Marisa Tomei, claiming that George and Elaine are meeting to discuss a problem with her boyfriend so that Susan does not think that George is having an affair ("The Cadillac"). George also uses the pseudonym when interviewing for a job with Elaine's boss in "The Red Dot". When asked which authors he reads, the answer is "Art Vandelay" from New York. In "The Serenity Now", George calls up fake customers, one of whom is "Mr. Vandelay", pretending to get computer orders. In "The Bizarro Jerry", George goes to an office and asks for Mr. Vandelay as part of a setup to approach an attractive secretary. Finally, in "The Puerto Rican Day", George pretends to be Vandelay (along with Jerry as Kal Varnsen and Kramer as H.E. Pennypacker) to try to sneak into an open house to watch a Mets game that they had left because the team was getting blown out. In the episode "The Finale", the name of the presiding judge is actually Arthur Vandelay, much to George's amazement. George says he thinks it is "good luck" that that is the judge's name, though this turns out not to be true.

During the seventh season ("The Pool Guy"), George reveals he has two distinct personas, Relationship George and Independent George. Relationship George, he explains, is the conscientious personality he feels forced to adopt in the presence of his fiancée, Susan. Independent George, on the other hand, is the "real" George. Independent George is composed of a subset of personalities, such as Movie George, Coffee Shop George, Liar George, and Bawdy George. Independent George is the George that Jerry knows and grew up with. George worries that if Susan starts socializing with the group, his two worlds will irrevocably collide, resulting in Relationship George "killing" Independent George. Paraphrasing Abraham Lincoln, he declares, "A George divided against itself cannot stand!"

At one point ("The Maid"), George wants to be known as "T-Bone", but his co-workers at Kruger Industrial Smoothing nickname him "Koko" because of the way he had flailed his arms when demanding the nickname "T-Bone" back from a coworker. George deliberately hires a woman named Coco to work there, only to be nicknamed Gammy instead.

Biff Loman: In "The Subway", this name is used for George by Jerry in reference to the character of the same name from Arthur Miller's Death of a Salesman. George is on the way to a job interview, and Jerry tells him not to whistle in the elevator like Biff did in the play. After a series of events throughout the episode, George arrives at the coffee shop wearing only a bed sheet in a toga-like fashion, to which Jerry says, "What happened, Biff? Did you whistle on the elevator?" George is also referred to as Biff by the daughter of his unemployment agent in "The Boyfriend" and by Jerry in both "The Pez Dispenser" and "The Visa".

^Davies, Dan (October 16, 2004). "Unhappy as Larry". The Guardian. Retrieved August 3, 2009. Spotters will know that Jason Alexander's character in Seinfeld, the stooge George Costanza, is largely based on the real Larry David